The range of birth dates above is taken from the authority file of the Bibliothèque nationale, which gives the place of J’s birth and death as Valladolid. Lorca is more cautious, dating his birth to sometime in the first half of the 16th century, not giving a place of his death, but settling on 1562 for his death date, one higher than that of the Bibliothèque nationale. J. was a member of a well-known Spanish noble family. His father had served Isabel la Católica, and various members of the family were prominent into the 18th century. J. received his formation at Salamanca, and he briefly taught Justinian’s Institutes there and at Valladolid. He served as a prosecutor and an auditor of the Real Chancillería of Granada rising to the level of magistrado in 1551. He became auditor of the Real Chancillería of Valladolid in 1554, a position that he held until his death in 1562.

J’s chief claim to fame is his De Nobilitatis et immunitatis Hispaniae causis (quas hidalguia appellant) deque Regalium Tributorum (quos pechos dicunt) iure, ordine iudicio et excusatione summa seu tractatus first published in Granada in 1553. An expanded edition appeared in Salamanca under the title Summa nobilitatis hispanicae et inmunitatis regiorum tributorum: causas, ius, ordinem, iudicium et excusationem breviter complectens in 1559, and from this are derived the posthumous editions of Salamanca 1570, TUI 1584 (t. 16), and Madrid 1612. In this work J. brings a full panoply of humanistic learning to bear on a justification of the privileges of the nobility, not on the basis of the accident of their birth but on the basis of their character.